Thermoplastic elastomers and process for making same

ABSTRACT

A process for producing a thermoplastic elastomer composition, the process comprising synthesizing an elastomeric copolymer by polymerizing ethylene, an α-olefin, and optionally a diene monomer within the gas phase to thereby produce a gas-phase elastomeric copolymer, blending the gas-phase elastomeric copolymer with a thermoplastic polymer to form a mix of the elastomeric copolymer and thermoplastic polymer, and dynamically vulcanizing the gas-phase elastomeric copolymer within the mix of the elastomeric copolymer and thermoplastic polymer.

This application gains priority from U.S. Provisional Application No.60/349,099, filed on Jan. 15, 2002.

TECHNICAL FIELD

This invention relates to thermoplastic elastomers and processes formaking the same. These thermoplastic elastomers are efficiently producedand exhibit unique properties due to the use of a gas-phase polymerizedelastomeric copolymer.

BACKGROUND OF THE INVENTION

Thermoplastic elastomers are known. They have many of the properties ofthermoset elastomers, yet they are processable as thermoplastics. Onetype of thermoplastic elastomer is a thermoplastic vulcanizate, whichmay be characterized by finely-divided rubber particles dispersed withina plastic. These rubber particles are crosslinked to promote elasticity.Thermoplastic vulcanizates are conventionally produced by dynamicvulcanization, which is a process whereby a rubber is cured orvulcanized within a blend with at least one non-vulcanizing polymerwhile the polymers are undergoing mixing or masticating at some elevatedtemperature, preferably above the melt temperature of thenon-vulcanizing polymer.

Many conventionally produced thermoplastic vulcanizates employ anethylene-propylene-diene terpolymer (EPDM) as the rubber of choice.These terpolymers have typically been synthesized by using solutionpolymerization techniques. A shortcoming of solution polymerization isthe inability to synthesize high molecular weight polymer (e.g., M_(w)of 500,000 or more) without oil extending the polymer product. The sameshortcomings exist when slurry polymerization techniques are used.Because the use of high molecular weight EPDM rubber is desirable in themanufacture of technologically useful thermoplastic vulcanizates, oilextended EPDM is often used. And, as a result, the oil that is employedto extend the EPDM ultimately becomes part of the thermoplasticvulcanizate. The ability to select an oil during manufacture of thethermoplastic vulcanizate is therefore limited. This can bedisadvantageous because it is often desirable to tailor the performancecharacteristics of the thermoplastic vulcanizate with various oils.

Furthermore, conventional solution-polymerization techniques producerubber bales, and these bales are then pre-processed by granulating therubber prior to manufacture of the thermoplastic vulcanizate. Thisadditional manufacturing step can be energy intensive, time consuming,costly, and involves additional process complications.

Conventionally produced thermoplastic vulcanizates also typicallyinclude carbon black. Although carbon black is typically added to thecomposition prior to dynamic vulcanization, conventional wisdom suggeststhat the carbon black becomes primarily incorporated into the plasticmatrix of the thermoplastic vulcanizate. As a result, the advantagesassociated with carbon black, such as the UV stability, are not believedto be fully realized in the rubber phase.

Because the number of uses of thermoplastic vulcanizates is increasing,the performance demands that are placed on these materials is moredemanding, and the manufacturing efficiency of the materials iscontinually pursued, there exists a need to overcome some of theshortcomings associated with the prior art materials and methods ofmanufacture.

SUMMARY OF INVENTION

In general the present invention provides a process for producing athermoplastic elastomer composition, the process comprising synthesizingan elastomeric copolymer by polymerizing ethylene, an α-olefin, andoptionally a diene monomer within the gas phase to thereby produce agas-phase elastomeric copolymer, blending the gas-phase elastomericcopolymer with a thermoplastic polymer to form a mix of the elastomericcopolymer and thermoplastic polymer, and dynamically vulcanizing thegas-phase elastomeric copolymer within the mix of the elastomericcopolymer and thermoplastic polymer.

The present invention further provides a process for producing athermoplastic elastomer composition, the process comprising providing agranular elastomeric copolymer having dispersed therein carbon black,where the granular elastomeric copolymer is synthesized by usinggas-phase polymerization, and dynamically vulcanizing the granularelastomeric copolymer within a blend that includes the elastomericcopolymer and a thermoplastic polymer.

The present invention also includes a thermoplastic elastomercomposition comprising a blend of a vulcanized elastomeric copolymer anda thermoplastic polymer, where said vulcanized elastomeric copolymerderives from the vulcanization of an elastomeric copolymer that wassynthesized by using gas-phase polymerization techniques, and where thevulcanized elastomeric copolymer and the thermoplastic polymer havecarbon black dispersed therein.

The use of gas-phase synthesized elastomeric copolymer, e.g.,ethylene-propylene-diene terpolymer, in thermoplastic vulcanizates hasunexpectedly solved many problems that were associated with the use ofsolution-synthesized elastomeric copolymers. To begin with, gas-phasesynthesis can provide high molecular weight copolymers that are granularand not oil extended. As a result, technologically useful thermoplasticvulcanizates can be efficiently produced with an oil of choice.Furthermore, the fact that the gas-phase synthesized elastomericcopolymers are granular thereby provides the ability to eliminatecertain processing steps during the manufacture of thermoplasticvulcanizates. And, different levels of oil incorporation can be achievedwhen certain oils are blended with the granular polymer. Further, thesynthesis of gas-phase elastomeric copolymers can employ various inertmaterials, such as carbon black, as dispersants, and as a result, theseinert materials are evenly dispersed throughout the polymer.Advantageously, when gas-phased synthesized elastomeric copolymershaving carbon black dispersed therein are employed in the manufacture ofthermoplastic vulcanizates, the UV stability provided by the carbonblack can, in certain embodiments, advantageously exist in both therubber and plastic phases of the thermoplastic vulcanizate. Also, it hasadvantageously been found that the carbon black within the rubber canprovide thermoplastic vulcanizates having a technologically useful UVstability without the need for adding additional carbon black during themanufacture of the thermoplastic vulcanizate. Still further, thepredispersed carbon black is believed to contribute to better extrusionquality of the thermoplastic vulcanizate.

PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION

The thermoplastic elastomers of this invention include a blend of anelastomeric copolymer and a non-vulcanizing polymer such as athermoplastic polymer. The preferred elastomeric copolymer is obtainedfrom the polymerization of ethylene, and α-olefin, and optionally adiene monomer by using gas-phase polymerization techniques. Theelastomeric copolymers are advantageously granular and preferably haveinert material such as carbon black evenly dispersed therein. Thesecopolymers may be referred to as gas-phase elastomeric copolymers.

Gas-phase elastomeric copolymers include polymeric units deriving fromethylene, an α-olefin, and optionally a diene monomer. These monomersare preferably polymerized by using gas-phase polymerization techniques.These techniques are well known in the art as described in U.S. Pat.Nos. 5,783,645 and 6,011,128, which are incorporated herein byreference.

The α-olefins may include, but are not limited to, propylene, 1-butene,1-hexene, 4-methyl-1 pentene, 1-octene, 1-decene, or combinationsthereof. The preferred α-olefins are propylene, 1-hexene, 1-octene orcombinations thereof.

The diene monomers may include, but are not limited to,5-ethylidene-2-norbornene; 1,4-hexadiene; 5-methylene-2-norbornene;1,6-octadiene; 5-methyl-1,4-hexadiene; 3,7-dimethyl-1,6-octadiene;1,3-cyclopentadiene; 1,4-cyclohexadiene; dicyclopentadiene;5-vinyl-2-norbornene, divinyl benzene, and the like, or a combinationthereof. The preferred diene monomers are 5-ethylidene-2-norbornene and5-vinyl-2-norbornene. In the event that the copolymer is prepared fromethylene, α-olefin, and diene monomers, the copolymer may be referred toas a terpolymer or even a tetrapolymer in the event that multiplex-olefins or dienes are used. The preferred elastomeric copolymersinclude terpolymers of ethylene, propylene, and5-ethylidene-2-norbornene.

The elastomeric copolymers contain from about 20 to about 90 molepercent ethylene units deriving from ethylene monomer. Preferably, thesecopolymers contain from about 40 to about 85 mole percent, and even morepreferably from about 50 to about 80 mole percent, ethylene units.Furthermore, where the copolymers contain diene units, the diene unitscan be present in an amount from about 0.1 to about 5 mole percent,preferably from about 0.2 to about 4 mole percent, and even morepreferably from about 1 to about 2.5 mole percent. The balance of thecopolymer will generally be made up of units deriving from α-olefinmonomers. Accordingly, the copolymer may contain from about 10 to about80 mole percent, preferably from about 15 to about 50 mole percent, andmore preferably from about 20 to about 40 mole percent, α-olefin unitsderiving from α-olefin monomers. The foregoing mole percentages arebased upon the total moles of the polymer.

Elastomeric copolymers employed in this invention can be synthesized ina gas-phase fluidized bed reactor, as disclosed in U.S. Pat. Nos.4,379,558, 4,383,095, 4,521,566, 4,876,320, 4,994,534, 5,317,036,5,453,471, 5,648,442, 6,228,956, and 6,028,140, which are incorporatedherein by reference. They can likewise be synthesized in a gas-phasestirred reactor as disclosed in U.S. Pat. No. 3,256,263, which isincorporated herein by reference. These gas-phase polymerizationprocesses can be conducted in the condensed mode, induced condensedmode, or liquid monomer mode, all of which are known in the art.

The catalyst employed to polymerize the ethylene, α-olefin, and dienemonomers into elastomeric copolymers can include both traditionalZiegler-Natta type catalyst systems, especially those including vanadiumcompounds, as disclosed in U.S. Pat. No. 5,783,64, as well asmetallocene catalysts, which are also disclosed in U.S. Pat. No.5,793,645. Other catalysts systems such as the Brookhardt catalystsystem may also be employed.

Preferably, the elastomeric copolymers are produced in the presence ofan inert particulate matter such as carbon black, silica, clay, talc, orthe like, as described in U.S. Pat. No. 4,994,534, which is incorporatedherein by reference. The preferred inert particulate material is carbonblack.

The gas-phase elastomeric copolymers preferably have a weight averagemolecular weight (M_(w)) that is greater than about 200,000, morepreferably from about 300,000 to about 1,000,000, even more preferablyfrom about 400,000 to about 900,000, and still more preferably fromabout 500,000 to about 700,000. These copolymers preferably have anumber average molecular weight (M_(n)) that is greater than about80,000, more preferably from about 100,000 to about 350,000, even morepreferably from about 120,000 to about 300,000, and still morepreferably from about 130,000 to about 250,000. Advantageously, the useof gas-phase elastomeric copolymers allows high molecular weightcopolymer, as described above, to be employed without oil extension.

Useful gas-phase elastomeric copolymers preferably have a MooneyViscosity (ML(1+4@125° C.)) of from about 80 to about 450, morepreferably from about 200 to about 400, and even more preferably fromabout 300 to about 380, where the Mooney Viscosity is that of the neatpolymer.

The gas-phase elastomeric copolymers are advantageously granular.Preferably, the particle size of the granules is from about 0.4 to about1.0 mm, more preferably from about 0.5 to about 0.9 mm, and even morepreferably from about 0.6 to about 0.8 mm.

Because an inert particulate material is employed during the gas-phasesynthesis of the elastomeric copolymers, the resulting elastomericcopolymer granules will contain dispersed therein or coated thereon theinert particulate material. In a preferred embodiment, where carbonblack is employed as the inert particulate material, the resultingelastomeric copolymer granules will include from about 10 to about 40parts by weight carbon black per 100 parts by weight rubber, morepreferably from about 12 to about 30 parts by weight carbon black per100 parts by weight rubber, and more preferably from about 15 to about25 parts by weight carbon black per 100 parts by weight rubber.

The thermoplastic elastomers of this invention may also includeconventional elastomeric copolymers. These copolymers are typicallysolution or slurry polymerized. Examples of these elastomeric copolymersinclude rubbery copolymers polymerized from ethylene, at least onealphaolefin monomer, and at least one diene monomer, as well as butylrubber, which refers to a rubbery amorphous copolymer of isobutylene andisoprene or an amorphous terpolymer of isobutylene, isoprene, and adivinyl aromatic monomer. The conventional elastomeric copolymers arenormally not in granular form and do not have dispersed therein an inertmaterial as a direct result of the manufacturing or synthesis of thepolymer. These copolymer are well known in the art as disclosed in U.S.Pat. Nos. 4,130,535 and 6,451,915, which are incorporated herein byreference.

The thermoplastic polymer is a solid, generally high molecular weightplastic material, which may be referred to as a thermoplastic resin.Preferably, this resin is a crystalline or a semi-crystalline polymer,and more preferably is a resin that has a crystallinity of at least 25percent as measured by differential scanning calorimetry. Polymers witha high glass transition temperature are also acceptable as thethermoplastic resin. The melt temperature of these resins shouldgenerally be lower than the decomposition temperature of the rubber.Reference to a thermoplastic resin will include a thermoplastic resin ora mixture of two or more thermoplastic resins.

The thermoplastic resins preferably have a weight average molecularweight (M_(w)) from about 200,000 to about 700,000, and a number averagemolecular weight (M_(n)) from about 80,000 to about 200,000. Morepreferably, these resins have a M_(w) from about 300,000 to about600,000, and a M_(n) from about 90,000 to about 150,000.

The thermoplastic resins generally have a melt temperature (T_(m)) thatis from about 150 to about 175° C., preferably from about 155 to about170° C., and even more preferably from about 160 to about 170° C. Theglass transition temperature (T_(g)) of these resins is from about −5 toabout 10° C., preferably from about −3 to about 5° C., and even morepreferably from about 0 to about 2° C. The crystallization temperature(T_(c)) of these resins is from about 95 to about 130° C., preferablyfrom about 100 to about 120° C., and even more preferably from about 105to about 115° C. as measured by DSC and cooled at 10° C./min.

The thermoplastic resins generally have a melt flow rate that is lessthan about 10 dg/min, preferably less than about 2 dg/min, and stillmore preferably less than about 0.8 dg/min. Melt flow rate is a measureof how easily a polymer flows under standard pressure, and is measuredby using ASTM D-1238 at 230° C. and 2.16 kg load.

Exemplary thermoplastic resins include crystallizable polyolefins,polyimides, polyesters(nylons), poly(phenylene ether), polycarbonates,styrene-acrylonitrile copolymers, polyethylene terephthalate,polybutylene terephthalate, polystyrene, polystyrene derivatives,polyphenylene oxide, polyoxymethylene, and fluorine-containingthermoplastics. The preferred thermoplastic resins are crystallizablepolyolefins that are formed by polymerizing α-olefins such as ethylene,propylene, 1-butene, 1-hexene, 1-octene, 2-methyl-1-propene,3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene, and mixturesthereof. Copolymers of ethylene and propylene or ethylene or propylenewith another α-olefin such as 1-butene, 1-hexene, 1-octene,2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene,5-methyl-1-hexene or mixtures thereof is also contemplated. Thesehomopolymers and copolymers may be synthesized by using anypolymerization technique known in the art such as, but not limited to,the “Phillips catalyzed reactions,” conventional Ziegler-Natta typepolymerizations, and metallocene catalysis including, but not limitedto, metallocene-alumoxane and metallocene-ionic activator catalysis.

An especially preferred thermoplastic resin is high-crystallineisotactic or syndiotactic polypropylene. This polypropylene generallyhas a density of from about 0.85 to about 0.91 g/cc, with the largelyisotactic polypropylene having a density of from about 0.90 to about0.91 g/cc. Also, high and ultra-high molecular weight polypropylene thathas a fractional melt flow rate is highly preferred. These polypropyleneresins are characterized by a melt flow rate that is less than or equalto 10 dg/min and more preferably less than or equal to 1.0 dg/min perASTM D-1238.

Any curative that is capable of curing or crosslinking the elastomericcopolymer may be used. Some non-limiting examples of these curativesinclude phenolic resins, peroxides, maleimides, and silicon-containingcuratives.

Any phenolic resin that is capable of crosslinking a rubber polymer canbe employed in practicing the present invention. U.S. Pat. Nos.2,972,600 and 3,287,440 are incorporated herein in this regard. Thepreferred phenolic resin curatives can be referred to as resole resinsand are made by condensation of alkyl substituted phenols orunsubstituted phenols with aldehydes, preferably formaldehydes, in analkaline medium or by condensation of bi-functional phenoldialcohols.The alkyl substituents of the alkyl substituted phenols typicallycontain 1 to about 10 carbon atoms. Dimethylol phenols or phenolicresins, substituted in para-positions with alkyl groups containing 1 toabout 10 carbon atoms are preferred. These phenolic curatives aretypically thermosetting resins and may be referred to as phenolic resincuratives or phenolic resins. These phenolic resins are ideally used inconjunction with a catalyst system. For example, non-halogenated phenolcuring resins are preferably used in conjunction with halogen donorsand, optionally, a hydrogen halide scavenger. Where the phenolic curingresin is halogenated, a halogen donor is not required but the use of ahydrogen halide scavenger, such as ZnO, is preferred. For a furtherdiscussion of phenolic resin curing of thermoplastic vulcanizates,reference can be made to U.S. Pat. No. 4,311,628, which is incorporatedherein by reference.

An example of a preferred phenolic resin curative is defined accordingto the general formula (I).

where Q is a divalent radical selected from the group consisting of—CH₂—, —CH₂—O—CH₂—; m is zero or a positive integer from 1 to 20 and R′is an organic radical. Preferably, Q is the divalent radical—CH₂—O—CH₂—, m is zero or a positive integer from 1 to 10, and R′ is anorganic radical having less than 20 carbon atoms. Still more preferablym is zero or a positive integer from 1 to 5 and R′ is an organic radicalhaving between 4 and 12 carbon atoms.

Peroxide curatives are generally selected from organic peroxides.Examples of organic peroxides include, but are not limited to,di-tert-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide,α,α-bis(tert-butylperoxy)diisopropyl benzene, 2,5 dimethyl2,5-di(t-butylperoxy)hexane, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, benzoyl peroxide, lauroyl peroxide, dilauroyl peroxide,2,5-dimethyl-2,5-di(tert-butylperoxy)hexene-3, and mixtures thereof.Also, diaryl peroxides, ketone peroxides, peroxydicarbonates,peroxyesters, dialkyl peroxides, hydroperoxides, peroxyketals andmixtures thereof may be used. Coagents such as triallylcyanurate aretypically employed in combination with these peroxides. For a furtherdiscussion of peroxide curatives and their use for preparingthermoplastic vulcanizates, reference can be made to U.S. Pat. No.5,656,693, which is incorporated herein by reference. When peroxidecuratives are employed, the elastomeric copolymer will preferablyinclude 5-vinyl-2-norbornene and 5-ethylidene-2-norbornene as the dienecomponent.

Useful silicon-containing curatives generally include silicon hydridecompounds having at least two SiH groups. These compounds react withcarbon-carbon double bonds of unsaturated polymers in the presence of ahydrosilation catalyst. Silicon hydride compounds that are useful inpracticing the present invention include, but are not limited to,methylhydrogen polysiloxanes, methylhydrogen dimethyl-siloxanecopolymers, alkyl methyl polysiloxanes, bis(dimethylsilyl)alkanes,bis(dimethylsilyl)benzene, and mixtures thereof.

Preferred silicon hydride compounds may be defined by the formula

where each R is independently selected from alkyls containing 1 to 20carbon atoms, cycloalkyls containing 4 to 12 carbon atoms, and aryls, mis an integer having a value ranging from 1 to about 50, n is an integerhaving a value ranging from 1 to about 50, and p is an integer having avalue ranging from 0 to about 6.

As noted above, hydrosilation curing of the elastomeric polymer ispreferably conducted in the presence of a catalyst. These catalysts caninclude, but are not limited to, peroxide catalysts and catalystsincluding transition metals of Group VIII. These metals include, but arenot limited to, palladium, rhodium, and platinum, as well as complexesof these metals. For a further discussion of the use of hydrosilation tocure thermoplastic vulcanizates, reference can be made to U.S. Pat. Nos.5,936,028 6,251,998, and 6,150,464, which is incorporated herein byreference. When silicon-containing curatives are employed, theelastomeric copolymer employed will preferably include5-vinyl-2-norbornene as the diene component.

Another useful cure system is disclosed in U.S. Pat. No. 6,277,916 B1,which is incorporated herein by reference. These cure systems employpolyfunctional compounds such as poly(sulfonyl azide)s.

Plasticizers, extender oils, synthetic processing oils, or a combinationthereof may be employed in the compositions of the present invention.The extender oils may include, but are not limited to, aromatic,naphthenic, and paraffinic extender oils. Exemplary synthetic processingoils are polylinear α-olefins, polybranched α-olefins, and hydrogenatedpolyalphaolefins. The compositions of this invention may include organicesters, alkyl ethers, or combinations thereof. U.S. Pat. Nos. 5,290,886and 5,397,832 are incorporated herein in this regard. The addition ofcertain low to medium molecular weight organic esters and alkyl etheresters to the compositions of the invention dramatically lowers theT_(g) of the polyolefin and rubber components, and of the overallcomposition, and improves the low temperatures properties, particularlyflexibility and strength. These organic esters and alkyl ether estersgenerally have a molecular weight that is generally less than about10,000. It is believed that the improved effects are achieved by thepartitioning of the ester into both the polyolefin and rubber componentsof the compositions. Particularly suitable esters include monomeric andoligomeric materials having an average molecular weight below about2000, and preferably below about 600. The ester should be compatible, ormiscible, with both the polyolefin and rubber components of thecomposition; i.e. that it mix with the other components to form a singlephase. The esters found to be most suitable were either aliphatic mono-or diesters or alternatively oligomeric aliphatic esters or alkyl etheresters. Polymeric aliphatic esters and aromatic esters were found to besignificantly less effective, and phosphate esters were for the mostpart ineffective.

In certain embodiments of this invention, the thermoplastic vulcanizatemay likewise include a polymeric processing additive. The processingadditive employed is a polymeric resin that has a very high melt flowindex. These polymeric resins include both linear and branched moleculesthat have a melt flow rate that is greater than about 500 dg/min, morepreferably greater than about 750 dg/min, even more preferably greaterthan about 1000 dg/min, still more preferably greater than about 1200dg/min, and still more preferably greater than about 1500 dg/min. Meltflow rate is a measure of how easily a polymer flows under standardpressure, and is measured by using ASTM D-1238 at 230° C. and 2.16 kgload. The thermoplastic elastomers of the present invention may includemixtures of various branched or various linear polymeric processingadditives, as well as mixtures of both linear and branched polymericprocessing additives. Reference to polymeric processing additives willinclude both linear and branched additives unless otherwise specified.The preferred linear polymeric processing additives are polypropylenehomopolymers. The preferred branched polymeric processing additivesinclude diene-modified polypropylene polymers. Thermoplasticvulcanizates that include similar processing additives are disclosed inU.S. Pat. No. 6,451,915, which is incorporated herein by reference.

In addition to the thermoplastic resin, the thermoplastic elastomer,curatives and optional extender oils, the composition may also includereinforcing and non-reinforcing fillers, antioxidants, stabilizers,rubber processing oil, lubricants, antiblocking agents, anti-staticagents, waxes, foaming agents, pigments, flame retardants and otherprocessing aids known in the rubber compounding art. These additives cancomprise up to about 50 weight percent of the total composition. Fillersand extenders that can be utilized include conventional inorganics suchas calcium carbonate, clays, silica, talc, titanium dioxide, carbonblack, as well as organic and inorganic nanoscopic fillers. Fillers,such as carbon black, are preferably added in combination with a carriersuch as polypropylene. This invention advantageously provides theability to add filler, such as carbon black, together with the rubber aswell as together with a thermoplastic carrier such as polypropylene in asingle-pass or one-step process.

Preferably, compositions of this invention will contain a sufficientamount of the elastomeric copolymer to form rubbery compositions ofmatter. The skilled artisan will understand that rubbery compositions ofmatter are those that have ultimate elongations greater than 100percent, and that quickly retract to 150 percent or less of theiroriginal length within about 10 minutes after being stretched to 200percent of their original length and held at 200 percent of theiroriginal length for about 10 minutes.

Accordingly, the thermoplastic elastomers of the present inventionshould comprise at least about 25 percent by weight elastomericcopolymer, preferably at least about 35 percent by weight elastomericcopolymer, even more preferably at least about 45 percent by weightelastomeric copolymer, and still more preferably at least about 50percent by weight elastomeric copolymer. More specifically, the amountof elastomeric copolymer within the thermoplastic vulcanizate isgenerally from about 25 to about 90 percent by weight, preferably fromabout 45 to about 85 percent by weight, and more preferably from about60 to about 80 percent by weight, based on the entire weight of thethermoplastic vulcanizate.

In one embodiment, the elastomeric copolymer component of thethermoplastic elastomers will consist entirely of the gas-phaseelastomeric copolymers. In other embodiments, the elastomeric copolymercomponent will include both gas-phase elastomeric copolymers as well asconventional elastomeric copolymers (e.g., solution-polymerizedelastomeric copolymer or slurry-polymerized elastomeric copolymer). Inthese latter embodiments, the elastomeric copolymer component mayinclude from about 10 to about 90 parts by weight of the gas-phaseelastomeric copolymer and from about 90 to about 10 parts by weight of aconventional elastomeric copolymer, preferably from about 20 to about 80parts by weight gas-phase elastomeric copolymer and from about 80 toabout 20 parts by weight conventional elastomeric copolymer, morepreferably from about 30 to about 70 parts by weight gas-phaseelastomeric copolymer and from about 70 to about 30 parts by weightconventional elastomeric copolymer, even more preferably from about 40to about 60 parts by weight gas-phase elastomeric copolymer and fromabout 60 to about 40 parts by weight conventional elastomeric copolymer,and still more preferably about 50 parts by weight gas-phase elastomericcopolymer and about 50 parts by weight conventional elastomericcopolymer, based on the entire weight of the elastomeric copolymer (orrubber component).

The thermoplastic elastomers should generally comprise from about 10 toabout 80 percent by weight of the thermoplastic resin based on the totalweight of the rubber and thermoplastic resin combined. Preferably, thethermoplastic elastomers comprise from about 15 to about 80 percent byweight, more preferably from about 20 to about 40 percent by weight, andeven more preferably from about 25 to about 35 percent by weight of thethermoplastic resin based on the total weight of the rubber andthermoplastic resin combined.

Where a phenolic resin curative is employed, a vulcanizing amountcurative preferably comprises from about 1 to about 20 parts by weight,more preferably from about 3 to about 16 parts by weight, and even morepreferably from about 4 to about 12 parts by weight, phenolic resin per100 parts by weight rubber.

The skilled artisan will be able to readily determine a sufficient oreffective amount of vulcanizing agent to be employed without unduecalculation or experimentation. The amount of vulcanizing agent shouldbe sufficient to at least partially vulcanize the elastomeric polymer.Preferably, the elastomeric polymer is completely vulcanized.

Where a peroxide curative is employed, a vulcanizing amount of curativepreferably comprises from about 1×10⁻⁴ moles to about 4×10⁻² moles, morepreferably from about 2×10⁻⁴ moles to about 3×10⁻² moles, and even morepreferably from about 7×10⁻⁴ moles to about 2×10⁻² moles per 100 partsby weight rubber.

Where silicon-containing curative is employed, a vulcanizing amount ofcurative preferably comprises from 0.1 to about 10 mole equivalents, andpreferably from about 0.5 to about 5 mole equivalents, of SiH percarbon-carbon double bond.

Generally, from about 5 to about 300 parts by weight, preferably fromabout 30 to about 250 parts by weight, and more preferably from about 70to about 200 parts by weight, of extender oil per 100 parts rubber isadded. The quantity of extender oil added depends upon the propertiesdesired, with the upper limit depending upon the compatibility of theparticular oil and blend ingredients; this limit is exceeded whenexcessive exuding of extender oil occurs. The amount of esterplasticizer in the composition will generally be less than about 250parts, and preferably less than about 175 parts, per 100 parts rubber.

When employed, the thermoplastic elastomers should generally comprisefrom about 1 to about 25 percent by weight of the polymeric processingadditive based on the total weight of the rubber and thermoplastic resincombined.

Preferably, the thermoplastic elastomers comprise from about 1.5 toabout 20 percent by weight, and more preferably from about 2 to about 15percent by weight of the polymeric processing additive based on thetotal weight of the rubber and thermoplastic resin combined.

Fillers, such as carbon black or clay, may be added in amount from about10 to about 250, per 100 parts by weight of rubber. The amount of carbonblack that can be used depends, at least in part, upon the type ofcarbon black and the amount of extender oil that is used. The amount ofextender oil depends, at least in part, upon the type of rubber. Highviscosity rubbers are more highly oil extendable.

Preferably, the rubber is crosslinked by dynamic vulcanization. The termdynamic vulcanization refers to a vulcanization or curing process for arubber contained in a thermoplastic elastomer composition, wherein therubber is vulcanized under conditions of high shear at a temperatureabove the melting point of the polyolefin component. The rubber is thussimultaneously crosslinked and dispersed as fine particles within thepolyolefin matrix, although other morphologies may also exist. Dynamicvulcanization is effected by mixing the thermoplastic elastomercomponents at elevated temperature in conventional mixing equipment suchas roll mills, Banbury mixers, Brabender mixers, continuous mixers,mixing extruders and the like. One method for preparing thermoplasticvulcanizates is described in U.S. Pat. No. 4,594,390, which isincorporated herein by reference, although methods employing low shearrates can also be used. For example, U.S. Pat. No. 4,594,390 includesthe preparation of a thermoplastic vulcanizate by using a high speedinternal mixer operating at a shear rate of at least 2000 sec⁻¹.

Those ordinarily skilled in the art will appreciate the appropriatequantities, types of cure systems, and vulcanization conditions requiredto carry out the vulcanization of the rubber. The rubber can bevulcanized by using varying amounts of curative, varying temperatures,and a varying time of cure in order to obtain the optimum crosslinkingdesired. Because the conventional elastomeric copolymers are notgranular and do not include inert material as part of the manufacturingor synthesis of the polymer, additional process steps must be includedto granulate or add inert material, if desired, to the conventionalelastomeric copolymer. On the other hand, gas-phase elastomericcopolymers are granular and include particulate material, such as carbonblack, and therefore the manufacture of thermoplastic vulcanizates fromthese elastomeric copolymers does not require, i.e., can be devoid of anelastomeric copolymer granulation step or a step of pre-dispersing inertmaterial, such as carbon black, into the elastomeric copolymer.

Despite the fact that the rubber component is partially or fully cured,the compositions of this invention can be processed and reprocessed byconventional plastic processing techniques such as extrusion, injectionmolding, and compression molding. The rubber within these thermoplasticelastomers is usually in the form of finely-divided and well-dispersedparticles of vulcanized or cured rubber, although a co-continuousmorphology or a phase inversion is also possible.

The thermoplastic elastomer of this invention are useful for making avariety of articles such as weather seals, hoses, belts, gaskets,moldings, boots, elastic fibers and like articles. They are particularlyuseful for making articles by blow molding, extrusion, injectionmolding, thermo-forming, elasto-welding and compression moldingtechniques. More specifically, they are useful for making vehicle partssuch as weather seals, brake parts such as cups, coupling disks, anddiaphragm cups, boots such as constant velocity joints and rack andpinion joints, tubing, sealing gaskets, parts of hydraulically orpneumatically operated apparatus, o-rinǵs, pistons, valves, valve seats,valve guides, and other elastomeric polymer based parts or elastomericpolymers combined with other materials such as metal/plastic combinationmaterials. Also contemplated are transmission belts including V-belts,toothed belts with truncated ribs containing fabric faced V's, groundshort fiber reinforced V's or molded gum with short fiber flocked V's.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested. The examples shouldnot, however, be viewed as limiting the scope of the invention. Theclaims will serve to define the invention.

General Experimentation

Samples 1-8

Thermoplastic vulcanizates were prepared by employing eithersolution-synthesized EPDM or gas-phase polymerized EPDM. Table Iprovides the characteristics of the various EPDMs.

TABLE I EPDM I EPDM II EPDM III EPDM IV Synthesis Method solutionsolution gas-phase gas-phase Catalyst vanadium- vanadium- metallocenevanadium based based Mooney 50 91 80 84 (ML₁₊₄@125° C.) Ethylene Weight% 64 55.5 68 64.2 Propylene Weight % 32.1 38.8 28 32.3 5-ethylidene-2-3.9 5.7 4.0 3.5 norbornene Weight % Molecular Weight — — — — (GPC) M_(n)150,000 81,900 — — M_(w) 450,000 288,000 — — Oil (parts/100 parts 75 0 00 rubber) Carbon Black (parts/ 0 0 18-30 18-30 100 parts rubber)

The thermoplastic vulcanizates were prepared by using large-scale highshear mixers and the method as set forth in U.S. Pat. No. 4,594,390. Theingredients used in each thermoplastic vulcanizate are disclosed inTable II together with physical testing that was performed on Samplesthat were molded at 190° C. In addition to the ingredients set forth inTable II, each thermoplastic vulcanizate included 42.78 parts by weightclay per 100 parts by weight rubber, 3.4 parts by weight wax per 100parts by weight rubber, 1.94 parts by weight zinc oxide per 100 parts byweight rubber, 1.26 parts by weight stannous chloride per 100 parts byweight rubber, and 4.4 parts by weight phenolic resin per 100 parts byweight rubber.

TABLE II 1 2 3 4 5 6 7 8 EPDM I 175 175 175 — — — — — EPDM II — — — — —— — 100 EPDM III — — — 118 118 118 118 — Polypropylene I 36.9 — — 36.636.6 30.6 — 36.6 Polypropylene II — — — 6.7 6.7 6.7 6.7 — PolypropyleneIII — — — — — 6 6 — Polypropylene IV — 36.9 — — — — — — Polypropylene V— — 36.9 — — — 30.6 — Carbon Black (40% active) 24.4 24.4 24.4 — — — — —Processing Oil 59.9 59.9 59.9 134.9 134.9 134.9 134.9 134.9 Moisture (%)0.043 0.06 0.045 0.071 0.034 0.036 0.066 0.037 Hardness (Shore A) 69.467.8 67.3 62.5 61.7 62.1 62.2 65.1 Specific Gravity 0.99 0.958 1.0090.998 0.986 0.998 0.998 0.961 Ultimate Tensile Strength (MPa) 7.05 6.616.91 5.26 5.34 4.80 5.12 5.10 Ultimate Elongation (%) 450 448 424 341357 335 343 299 M 100 (MPa) 2.63 2.36 2.78 2.16 2.01 1.99 1.99 2.32Weight Gain (%) 79 84 87 87 88 88 83 82 LCR (Pa · s @ 1200 S⁻¹ @ 204°C.) 85.1 89.7 92.2 86.6 83.9 82.7 88.9 85.2 ESR 70 90 70 88 89 106 89122 Tension Set (%) 10 8 10 9.5 9.5 9.5 9.5 15 Spot Count 84 >100 >10051 10 12 6 >100 UV @ 2,500 kJ (ΔE) 0.93 0.96 — 1.12 1.08 1.03 — —

The clay employed was obtained under the tradename ICECAP K (Burgess),the carbon black was obtained under the tradename AMPACET 49974 (whichcontains about 40% by weight carbon black and about 60% by weightpolypropylene as a carrier), the processing oil was obtained under thetradename SUNPAR 150M, the wax was obtained under the tradename OKERIN™wax, and the phenolic resin was obtained under the tradename SP1045(Schenectady Int., Schenectady, N.Y.). Polypropylene I was obtainedunder the tradename D008M (Aristech), which has an MFR of about 0.8dg/min, Polypropylene II was obtained under the tradename FP230(Aristech), which has an MFR of about 30 dg/min, Polypropylene III wasobtained under the tradename 3746G (Exxon), which has an MFR of about1,200 dg/min, Polypropylene IV was obtained under the tradename 51S07A(Equistar), which has an MFR of about 0.7 dg/min, and Polypropylene Vwas obtained under the tradename TR 477 (Equistar), which has an MFR ofabout 0.5 dg/min.

Samples 9-18

In a similar fashion to Samples 1-8, additional thermoplasticvulcanizates were prepared by using both solution-polymerized orsynthesized and gas-phase synthesized EPDM. Distinguishing ingredientsand the results of the physical testing of each thermoplasticvulcanizate is set forth in Table III.

TABLE III 9 10 11 12 13 EPDM I — — — — 175 EPDM II 100 100 100 100 100EPDM IV — — — — — Polypropylene IV 219.1 219.1 57 57 57 Carbon Black19.28 19.28 8.65 8.65 8.65 Phenolic Resin 6 6 5.5 5.5 5.5 Processing Oil130 110 130 110 55 Moisture (%) 0.013 0.019 0.02 0.018 0.015 Hardness,Shore A (D) (37)   (40) 73 75 76.8 Specific Gravity 0.955 0.963 0.970.968 0.891 Ultimate Tensile Strength (MPa) 12.51 13.56 6.94 7.29 7.95Ultimate Elongation (%) 637 637 299 320 436 M 100 (MPa) 7.64 8.38 3.053.26 3.19 Weight Gain (%) 67.5 69 73.5 88.5 72.5 ACR (Poise) 1465 21881873 188 659 ESR 78 36 209 68 64 Tension Set (%) 49.5 49 10.5 11.5 13 1415 16 17 18 EPDM I 175 — — — — EPDM II — — — — — EPDM IV — 118 118 118118 Polypropylene IV 219.1 57 57 219.1 219.1 Carbon Black 19.28 — — — —Phenolic Resin 6 5.5 5.5 6 6 Processing Oil 55 130 110 130 110 Moisture(%) 0.044 0.025 0.028 0.017 0.029 Hardness Shore A (D) (41.1) 73.1 77.140.7 43.6 Specific Gravity 0.952 0.99 1.0 0.966 0.969 Ultimate TensileStrength (MPa) 16.22 4.73 5.29 10.74 12.38 Ultimate Elongation (%) 590354 306 459 527 M 100 (MPa) 8.35 2.77 3.17 8.16 8.73 Weight Gain (%)44.5 93 102.5 49 50.5 ACR (Poise) 860 205 606 597 989 ESR 35 407 388 179247 Tension Set (%) 47 19.5 20.5 55 55Samples 19-20

In a similar fashion to Samples 1-18, a thermoplastic vulcanizate wasprepared by using solution-polymerized EPDM and comparing thisthermoplastic vulcanizate to a thermoplastic vulcanizate prepared byusing a blend of solution-polymerized EPDM and gas-phase synthesizedEPDM. Distinguishing ingredients and results of the analytical testingof the thermoplastic vulcanizates is set forth in Table IV.

TABLE IV 19 20 EPDM I 175 87.5 EPDM III — 59 Polypropylene I 36.9 36.9Polypropylene II — 14.4 Carbon Black 24.4 0 Processing Oil 59.9 97.4Moisture (%) 0.028 0.038 Hardness (Shore A) 70.1 68 Specific Gravity0.991 0.964 Ultimate Tensile Strength (MPa) 7.39 6.47 UltimateElongation (%) 441 380 M 100 (MPa) 2.68 2.66 Weight Gain (%) 79 78.5 LCR(Pa · s @ 1200 s⁻¹ @ 204° C.) 92.7 82.4 ESR 77 75 Tension Set (%) 11.510.5 UV @ 2,500 kJ (ΔE) 0.86 0.80Samples 30-34

Four additional thermoplastic vulcanizates were prepared in a similarfashion to the previous samples except that the thermoplasticvulcanizates were dynamically cured by employing a peroxide cure systemat lower rates. In addition to the ingredients set forth in Table V,each thermoplastic vulcanizate included 42 parts by weight clay per 100parts by weight rubber.

TABLE V Samples 21 22 23 24 EPDM I 175 — — — EPDM III — 120 120 120Polypropylene IV 60 60 60 60 Peroxide (50% active) 6.60 3.30 6.60 9.00Coagent (50% active 6.60 6.60 6.60 9.00 Processing Oil 55 55 55 55Hardness (Shore A) 67 70 73 74 Specific Gravity 0.966 1.005 1.007 1.000Ultimate Tensile Strength (MPa) 5.86 6.57 8.12 6.04 Ultimate Elongation(%) 304 248 224 179 M 100 (MPa) 3.09 4.17 5.03 4.43 Weight Gain (%) 91114 82 92 Tension Set (%) 9.0 13.5 11.0 11.0

The peroxide was a 2,5-di(t-butylperoxy)hexane and the coagent wastriallylisocyanurate.

The analytical procedures employed to perform physical testing on eachthermoplastic vulcanizate sample included the following.

The surface spot count provides a quantitative measurement of thesurface spots of an extruded elastomeric strip through the use of avisual inspection standard. In performing the test, a 1 inch or 1½ inchdiameter extruder equipped with a 24:1 length/diameter screw having a3-3.5 compression ratio was used. The extruder is fitted with a stripdie that is 25.4 mm wide×0.5 mm thick×7-10 mm land length. A breakerplate is used with the die, but no screen pack is placed in front of thebreaker plate. In preparing the extrudate, a temperature profile isemployed to give a melt temperature of 200° C.±3° C. A hand-heldtemperature probe should be used to establish the melt temperature. Withthe extruder having three temperature zones within the feed zone, zone 1should be set to 180° C., zone 2 should be set to 190° C., and zone 3should be set to 200° C. The fourth zone, which is the die zone, shouldbe set to 205° C. These temperatures should be controlled to +/−6° C.When the zone temperatures have reached their set points, the screwshould be started and about 1 kg of the sample should be loaded into thefeed hopper. The extruder screw speed should be set to maintain anoutput of approximately 50 g+/−5 g per minute. The material should beallowed to flush through the extruder for at least five minutes beforecollecting any sample.

Extrusion surface roughness (ESR) was measured as described in ChemicalSurface Treatments of Natural Rubber And EPDM Thermoplastic Elastomers:Effects on Friction and Adhesion, RUBBER CHEMISTRY AND TECHNOLOGY, Vol.67, No. 4 (1994). The rating for each sample was determined by using astylus profilometer.

Shore A and D hardness were determined pursuant to ASTM D-2240-91 at 23°C. by using a durometer. Ultimate tensile strength, ultimate elongation,and 100 percent modulus were determined according to ASTM D-412-92 at23° C. by using an Instron Testing Machine. Weight gain was determinedaccording to ASTM D-471 after 24 hours at 125° C. Tension set wasdetermined according to ASTM D-142.

LCR capillary viscosity was determined by using a Dynisco analyzer andtheir recommended procedure. ΔE was determined according to SAE J1960(June 1989), which is the accelerated exposure of automotive exteriormaterials test using a controlled irradiance water-cooled xenon arcapparatus.

While the best mode and preferred embodiment of the invention have beenset forth in accord with the Patent Statues, the scope of this inventionis not limited thereto, but rather is defined by the attached claims.Thus, the scope of the invention includes all modifications andvariations that may fall within the scope of the claims.

1. A process for producing a thermoplastic elastomer composition, saidprocess comprising: providing a granular elastomeric copolymer havingdispersed therein carbon black, where said granular elastomericcopolymer is synthesized by using gas-phase polymerization; anddynamically vulcanizing the granular elastomeric copolymer within ablend that includes the elastomeric copolymer and a thermoplasticpolymer; where the Mooney Viscosity (ML(1+4@125° C.)) of the neatelastomeric copolymer is from about 200 to about
 450. 2. The process ofclaim 1, where said process is devoid of a step of granulating theelastomeric copolymer prior to said step of blending the elastomericcopolymer with the thermoplastic polymer.
 3. The process of claim 1,where the elastomeric copolymer includes from about 10 to about 40 partsby weight carbon per 100 parts by weight rubber.
 4. The process of claim1, where the elastomeric copolymer has a particle size of about 0.4 toabout 1.0 mm.
 5. The process of claim 1, where the blend also includes aconventionally synthesized elastomeric copolymer.
 6. The process ofclaim 1, where the elastomeric copolymer has a weight average molecularweight that is greater than about 200,000 and a number average molecularweight that is greater than about 80,000, and where the gas phaseelastomeric copolymer is non-oil extended.
 7. The process of claim 1,where said step of dynamically vulcanizing the gas phase elastomericcopolymer is achieved with a phenolic cure system or a peroxide curesystem.
 8. The process of claim 1, where the thermoplastic polymer ispolypropylene.